I know what you mean, this was my 3rd attempt at the ITF and they all failed because of people disappearing.
With my work hours, I don't get to play as much as I would like, and I do appreciate that people have RL to think about too. But I do echo you, in please don't start something you know you can't finish.
It happens. Some people underestimate the time taken to do a TF, others panic the first time they are defeated, others have unexpected real life issues that interfere.
I think we would have done it if just a couple more had stayed but that's the way it goes. Remember it's only a game 
I wouldn't worry too much about it. That's a reasonably popular TF, there will be plenty of opportunities to do it again.
I guess people leave TFs for a number of reasons. Some just can't help it... stuff in RL happens unavoidably.
Some people want the reward without the efforts sadly. The moment things get sticky they run and hide.
Some will give it a while but when things are perceived to be seen start going wrong it becomes tough to stick with it and of course as more people leave things get worse.
One of the problems I've encountered on the ITF and some of the tougher TFs is that people tend to get into arguments about "the best way" to complete the missions, and when they are forced by peer pressure to do things differently, it can be problematic.
But I bet you one thing: This was a PUG, not a group of people you regularly team with.
Thelonious Monk
Can anyone answer a small question for me?
Why do people start a TF then disappear and not return?
I was on the ITF on Friday and we started out with a full team - within an hour the leader left, for some reason then another 3 left as we got near the last mission. So it left 4/5 of us to try and complete it (not successful). In the end we gave up.
It was the first time I done that TF and for it to go like that I was so disappointed and annoyed at the members that up and left and didn't return.
Why start a long TF like that if you know you can't stay to the end?